Simplify extensions

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 4ab17fd85ae80d82273841ffc08296763631f019..789492fd95225965194b8262affc992978ea53de 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -609,8 +609,7 @@ namespace {
 
         // Can ttValue be used as a better position evaluation?
         if (ttValue != VALUE_NONE)
-            if (   ((tte->bound() & BOUND_LOWER) && ttValue > eval)
-                || ((tte->bound() & BOUND_UPPER) && ttValue < eval))
+            if (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER))
                 eval = ttValue;
     }
     else
@@ -830,13 +829,10 @@ moves_loop: // When in check and at SpNode search starts from here
                  || pos.is_passed_pawn_push(move)
                  || type_of(move) == CASTLE;
 
-      // Step 12. Extend checks and, in PV nodes, also dangerous moves
-      if (PvNode && dangerous)
+      // Step 12. Extend checks
+      if (givesCheck && pos.see_sign(move) >= 0)
           ext = ONE_PLY;
 
-      else if (givesCheck && pos.see_sign(move) >= 0)
-          ext = inCheck || ss->staticEval <= alpha ? ONE_PLY : ONE_PLY / 2;
-
       // Singular extension search. If all moves but one fail low on a search of
       // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
       // is singular and should be extended. To verify this we do a reduced search
@@ -949,8 +945,11 @@ moves_loop: // When in check and at SpNode search starts from here
           if (!PvNode && cutNode)
               ss->reduction += ONE_PLY;
 
+          else if (History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
+              ss->reduction += ONE_PLY / 2;
+
           if (move == countermoves[0] || move == countermoves[1])
-              ss->reduction = std::max(DEPTH_ZERO, ss->reduction-ONE_PLY);
+              ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
 
           Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
           if (SpNode)